Simultaneous removal of H{sub 2}S and NH{sub 3} in coal gasification processes. Final report

Nitrogen (N{sub 2}) occurs in coal in the form of tightly bound organic ring compounds, typically at levels of 1 to 2 wt.% on a dry-ash-free basis. During gasification, this fuel-bound nitrogen is released principally as ammonia. The formation of NH{sub 3} in coal gasification processes is a function of the coal N{sub 2} content and the gasifier operating conditions.During the use of coal gas to generate electricity in gas-fired turbines or molten carbonate fuel cells, fuel bound N{sub 2} is converted to nitrogen oxides (NO{sub x}), which are difficult to remove and are highly undesirable as atmospheric pollutants. Thus it is desirable to remove NH{sub 3} from coal gas in addition to other major contaminants such as hydrogen sulfide (H{sub 2}S) and particulates. The objective of this study was to develop a successful sorbent-catalyst combination of an NH{sub 3} decomposition catalyst with a zinc-based mixed-metal oxide H{sub 2}S sorbent with stable NH{sub 3} decomposition and H{sub 2}S removal efficiency under cyclic sulfidation-regeneration conditions in the temperature range of 500 to 700 C. Combining the NH{sub 3} and H{sub 2}S removal steps is expected to reduce capital and operating costs in an integrated gasification combined cycle (IGCC) power plant